1. Field of the Invention
This invention relates to a thermal re-radiation system and method of the general type employed to control, influence or alter the temperature of heated articles. While thermal systems constructed in accordance with the present invention and method of operation thereof may be employed in many other applications and for many other types of heated articles, for the purpose of describing the present invention its utilization in the operation of a hot strip rolling mill has been selected, as this to date is its preferred use.
2. Description of the Prior Art
It has long been recognized that the operation of hot strip rolling mills, and particularly that of the finishing train thereof, as well as the quality of the rolled product produced thereby can be improved by the employment of a means or system for controlling certain aspects of the temperature of the hot transfer bar. As used herein, the term "hot transfer bar" is meant to refer to the semi-rolled workpiece as it exits from the universal slab breakdown mill and before it is introduced into the finishing mill. An early U.S. Patent on the general subject may be found in U.S. Pat. No. 1,676,176 dated July 3, 1928, while several later U.S. Patents, which relate more specifically to some of the problems to which the present invention is addressed, are found in U.S. Pat. Nos. 3,344,648, 4,343,168, 4,463,585, 4,595,358 and 4,680,010 that issued between the years 1967 and 1987.
The more recent patents disclose the use of thermal insulating re-radiation heat shields which employ in combination with insulating fiber, metal hot faces designed to be arranged opposite the hot faces of the hot transfer bars. These patents attempt to utilize the heat shields to control the temperature and heat loss of the transfer bar prior to it being introduced into the finishing stand, two of the most important objectives being sought are the improvement in end to end gauge off the finishing mill and in the metallurgical properties of the rolled strip.
It has been found that heat shields and methods of their use of the above types and others do not acceptably function as intended and do not provide for maximum thermal effectiveness, nor are they cost effective. While there are other deficiencies in the known heat shields and methods, four of the most important are identified as follows: (1) reliance on the use of metallic hot faces that act as unfavorable heat sinks; (2) inability to provide a minimal air infiltration enclosure for the transfer bars, particularly as to the sides of the heat shields and the spaces between the driven rollers of the approach table arranged at the entry end of the first finishing stand for supporting and conveying the transfer bars; (3) inability to successfully protect the insulation of the lower heat shields from the water used to cool the bearings of the rollers; and (4) inability to provide a way to reduce heat build up in the rollers and heat transfer losses from the transfer bars. Another failure of prior heat shield systems employed in combination with hot strip rolling mill approach tables is the inability to provide an effective system for rolling grain oriented silicon steels where to obtain a optimum results the entry temperatures of the transfer bars not only must be maintained at a very high temperature but the end to end temperatures of the bars must be maintained at a minimum differential temperature.